The present invention relates to a planar object (single wafer) processing apparatus process which semiconductor wafers or some other singular object for processing, and in particular, relates to a heating and surface processing apparatus using lamp heating.
When semiconductor devices such as IC and LSI are manufactured, a semiconductor substrate of silicon or the like is repeatedly processed to form a required semiconductor on the wafer.
In such semiconductor wafer processing, processing such as the CVD method or the like is used to form a thin film on the wafer. With such processing, it is necessary to heat the entire surface of the wafer uniformly and to a required temperature so as to suitably grow a thin film on the wafer.
With such a wafer heating method, the methods of heating can be broadly divided into those by heaters and those by lamps. Lamp heating is widely used because it supplies heat energy as radiant waves in a vacuum and so the speed of temperature increase is not dependent upon the medium for heat transmission.
FIG. 16 shows an example of a wafer being heated by a conventional lamp.
A wafer 1 of silicon or the like is arranged in a vacuum container 2 (such as a CVD processing chamber), and a reactive gas such as silane or the like is supplied to the chamber 2. A lamp 8 having a reflector mirror 16 is fixed to the outside of the vacuum container 2 and irradiates parallel rays through a glass window 5 in a configuration where the wafer 1 is heated from underneath.
With heating by rays from such a lamp 8, the temperature of places where there are many incident rays is higher than other places and so it is difficult to have uniform heating for the entire wafer.
In order to solve this problem, it has been proposed that a susceptor 20 of silica glass, silica carbonate, carbon or the like be placed between the wafer 1 and the lamp 8. More specifically, the susceptor 20 is irradiated with and heated by the rays from the lamp 8 and the applied energy is converted into uniform heat energy which is then radiated to the wafer 1 to uniformly heat its entire surface.
According to a heating method using the radiant heat from such a susceptor 20, it is possible to have uniform heating for the entire surface of the susceptor 20 but it is necessary to have lamps having a large output capacity in order to heat the susceptor 20 and so there is a drop in the energy efficiency. In addition, the coefficient of heat transmission for the radiant heat differs according pressure of the reactive gas inside the vacuum container 2 and so the heating speed of the wafer 1 differs according to the reactive gas, and there is the problem that control of the temperature becomes difficult. In addition, since minute amounts of impurities such alkali metals are included in the susceptor 20, irradiation and heating by the rays from the lamp 8 causes the impurities inside the susceptor 20 to separate and float inside the vacuum container 2 to contaminate the wafer 1 which is being processed.
Furthermore, in CVD and other such processes, when there is a large change in the process, the heat escape from the wafer 1 differs according to the process and so there are instances where the pattern of irradiation has to be changed. However, the conventional method cannot correspond to such changes. In addition, the wafer 1 is supported inside the vacuum container 2 at the periphery of the wafer 1 by a pushpin, and is fixed by a clamp ring from above the peripheral of the wafer 1. However, the heat which is supplied from beneath escapes via this clamp ring and although the heat may be uniformly supplied to the entire surface of the wafer 1, there is the disadvantage that the temperature of the peripheral edge portion of the wafer 1 drops. In addition, the speed of heating at the peripheral edge portion of the wafer 1 becomes different from the speed of heating at a portion close to the center and so there is the danger that there will be differences in the amount of rays.
Not only this, performing uniform thin film growth on a wafer and using a CVD process requires that the source gas have a uniform distribution across the entire surface of the surface of the object of processing.
As shown in FIG. 17, a conventional sheet type (single wafer) CVD apparatus has a semiconductor wafer 104 or some other object of processing arranged under the central portion of a processing chamber 102 inside a process container 100, and this semiconductor wafer 104 is heated from underneath by a heater 106 while the source gas is blown onto the front surface of the semiconductor wafer 104 from many holes 108 above.
These holes 108 are provided as a large number of many through holes 108a provided to a circular plate having a diameter larger than the diameter of the semiconductor wafer 104 and so are part of a gas outlet 110a of a lower portion of a gas chamber 110 partitioned off from the processing chamber 102. The gas introduction chamber 112 which connects with the upper portion of this gas chamber 110 supplies a source gas which is to become an element of the composition of the film grown to the semiconductor wafer 104, from a gas supply source (not shown) and via the gas supply pipes 114, 116.
In the case when a tungsten film is to be grown on a wafer for example, WF.sub.6 gas which has been diluted to a required concentration by a carrier gas such as N.sub.2 gas is supplied from one gas supply pipe 114 at a required flow rate, while H.sub.2 gas to a required concentration is supplied at a required flow rate from the other gas supply pipe 116.
The WF.sub.6 gas, N.sub.2 gas and the H.sub.2 gas supplied from the gas supply pipe 114, 116 to the gas introduction chamber 112 having a comparatively small flow area is led to the gas chamber 110 having a relatively large flow path area and the gases mix together in this chamber. Then, the mixed source gases (WF.sub.6, N.sub.2, H.sub.2) are discharged from each of the holes 108a of the small hole plate 108 of the gas outlet 110a and are blown in the direction of the processing surface (upper surface) of the semiconductor wafer 104 immediately beneath them.
Moreover, even in the case of a conventional sheet type of plasma etching apparatus, a small hole plate and a gas chamber the same as those for the sheet-type CVD apparatus described above are used to blow an etching gas such as CF.sub.4 or the like onto an object of processing.
However, as described above, with a conventional type of plasma etching apparatus or sheet-type CVD apparatus, the process gas is blown from the gas chamber 110 via the small hole plate 108 so that the process gas is distributed uniformly across the entire surface of the surface of the object of processing.
However, with the conventional apparatus, when the process gas enters the gas chamber 110 having a large flow path area from the gas introduction chamber 112 having a comparatively small flow path area, the flow of the process gas is diffused in the horizontal direction and is disturbed, and gas eddies occur when the process gas is discharged from each of the through holes 108a of the small hole plate 108. In addition, the process gas flows into the gas introduction chamber with considerable force from the gas supply pipe but with a conventional apparatus, the process gas which flows into the gas introduction chamber 112 is immediately blown from the small hole plate 108 in that state and so this is another cause of gas eddies. Yet another cause of gas eddies is that the plural number of process gases are not properly mixed.
In this manner, in a conventional apparatus, it is difficult for a plural number of process gases which have been completely mixed to be blown uniformly onto an entire surface of a surface of an object of processing, and therefore it is difficult for there to be uniform film formation on a wafer.